<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <script src="./lib/vue.js"></script>
</head>
<body>
    <div id="box">{{str}}</div>
    <div id="root">{{str}}</div>

    </body>
<script>

  const vm1 = new Vue({
    el : '#box',
    data : {
        str : 'sxx'
    }
  });
  const vm2 = new Vue({
    el : document.querySelector('#box'),
      data : {
          str : 'dcl'
      }
  });

</script>
</html>